This invention relates to UV radiation protective coatings comprised of acrylic monomers or oligomers or mixtures thereof and an ultraviolet radiation absorber and thermoplastic articles coated with such coating.
Thermoplastics, such as polycarbonates, polyesters, polyvinyls, and the like are commercially important materials which are useful in a wide range of applications, from non-opaque impact resistant sheets to shaped articles. Many of these materials have rather low scratch resistance, are susceptible to attack by many common solvents and chemicals, and are subject to microcracking with aging and exposure, particularly exposure to ultraviolet light.
One process that has been used to overcome low scratch resistance and susceptibility to attack by solvents is the application of a durable coating to the plastic substrate. Typically, these coatings have been UV-curable, acrylate-based coatings. Moore, et al., U.S. Pat. No. 4,198,465, describe a polycarbonate article coated with a durably adherent mar, abrasion and chemical resistant UV cured coating. The coating is comprised of the photoreaction products of polyfunctional acrylate monomers and resorcinol monobenzoate. For some applications such as outdoor signs and the like, the UV absorber used in this coating, resorcinol monobenzoate, does not provide adequate protection of the polycarbonate substrate.
A need exists for UV-stabilized coating compositions which retain the advantageous physical and chemical properties of the base coating composition, and which retain their UV-absorbing characteristics at elevated temperatures.